Conventional motion picture film may include picture recording regions respectively arranged in a plurality of frames at an approximate mid-portion of the film and two series or rows of film take-up holes (perforations) respectively located on either side of each picture recording region. Such motion picture film may further include a linear analog sound track located between the picture recording regions and one row of the perforations which extends in a film take-up direction. Analog signals may be recorded onto such analog sound track by the use of analog recording techniques.
Due to the recent progress in digital technology, audio information or data associated with a motion picture may be digitally recorded onto a motion picture film. However, the recording position of the picture recording regions and the analog sound track are standardized by the Society Motion Picture and Television Engineers (SMPTE), an association in USA of motion picture and television engineers. As a result, digitized audio information or data is recorded in positions other than the picture recording regions and the analog sound track. More specifically, two digital sound tracks are provided in the film running direction of the motion picture film for recording digitized audio data therein and for reproducing the recorded digitized audio data therefrom. Each of such digital sound tracks is located between the perforations and a respective one of the lateral film edges. The audio data includes audio data for a right channel and audio data for a left channel which are each respectively recorded in a linear manner in one of the two digital sound tracks. Each of such audio data includes synchronization data, audio data and tracking patterns which are recorded in a direction normal to the film running direction in the digital sound tracks. The synchronization data or pattern is formed at the leading end of a block made up of a predetermined number of data followed by the audio data which is recorded block-by-block. The tracking patterns are recorded at each of the recording start and the recording end portions. Such tracking patterns are recorded in stripes on both sides of the digital sound tracks extending along the film running direction.
A reproducing apparatus for reproducing the digitized audio data from the motion picture film may include two CCD line sensors adapted for scanning the digital sound tracks so as to respectively read out the audio data recorded in the channels. Each of the CCD line sensors has a one-line reading region and is arranged so as to read such line in a direction normal to the film running or proceeding direction. Light out of a halogen lamp which is always turned on during reproduction is radiated from the back surface of the motion picture film. As a result, the synchronization data, audio data and the tracking patterns recorded on the digital sound tracks of the motion picture film are illuminated and radiated on the reading regions of each of the CCD line sensors.
The CCD line sensors have a function of so-called electronic shutter and are controlled so as to receive light for a predetermined time period. The CCD line sensors receive the illuminated synchronization data, audio data and the tracking patterns and convert them into electrical signals which are supplied to a data processor included in the reproducing apparatus. The data processor reproduces the audio data on a block basis in synchronization with the synchronization data and routes the reproduced audio data to a digital-to-analog (D/A) converter, which may be included in the reproducing apparatus, so as to convert the audio data to analog audio signals. Such analog audio signals may be thereafter supplied to a speaker unit. As a result, the speech corresponding to the digital audio data is provided by way of the speaker unit.
As previously described, the data processor receives signals corresponding to the tracking patterns from the CCD line sensors. Such signals are utilized by the data processor to provide tracking control data. More specifically, the tracking pattern is recorded at the recording start position and the recording end position for one-line of audio data. The data processor detects a level difference between, for example, the tracking pattern reproduced at the recording start position and that reproduced at the recording end position, so as to determine or detect a tracking error. The readout timing of the CCD line sensor is variably controlled in response to the tracking error. As a result, tracking error may be corrected so as to effect reproduction of the audio data at all times in the so-called just-track condition.
Heretofore, a halogen lamp has been used as a light source for reproducing audio data. However, the halogen lamp suffers from such defects as increased power consumption and heat evolution, such that heat radiating means have to be provided thus leading to an increased size of the apparatus and increased production cost. In addition, the halogen lamp has only a short service life and presents problems in operational reliability and increased labor in maintenance and management.
In addition, it has hitherto been practiced to keep the halogen lamp turned on at all times in order to reproduce audio data, so that it has been necessary to provide the above-mentioned CCD image sensor having the function of an electronic shutter. The function of the electronic shutter is to drain charges accumulated in respective pixels of the CCD image sensor by a drain pulse in order to adjust the charge accumulation time. There is now presented a problem that the charges drained by the drain pulse be fluctuated from pixel to pixel and that such fluctuations appear as an output noise in the CCD image sensor output. If the CCD image sensor output is subjected to such noise, the error rate is deteriorated and an abnormal noise is occasionally produced in the playback sound.